Generally the electrophotography processor comprises a charging device 5, developing device 20, transfer and separating unit 3, and cleaning unit 16 installed about a light-sensitive drum as shown in FIG. 1. In such a conventional electrophotography, the corona discharge generated from a corona wire 5' of the charging device being charged with high voltage current of about 6 KV makes the surface of the light-sensitive drum 4 charged with a given voltage. When the charged surface of the light-sensitive drum being exposed to the light emitted from a light-emitting device selectively, the portions of the surface exposed and not exposed have different voltages respectively, and accordingly the electrically latent image is formed on the surface. The light emitting device comprises a laser diode and an LED head array or a lamp. For example, in a copy machine, the light generated from the lamp is flashed on the manuscript and the surface of the light-sensitive drum is exposed to the light reflected from the manuscript. The electrostatic latent image of the light-sensitive drum is developed by the toner of a developing device 20. This developed image is transferred to the paper 2' transmitted from a paper cassette by a register roller 2. The residual toner on the light sensitive drum is eliminated by the cleaning device 16 and the transferred image on the paper is fixed by a fixing device 8. The numbers 9 and 10 are a discharging roller and a trays, respectively.
Generally in the prior art, the electrophotography processor incorporates a monolithic body comprising a light-sensitive drum, a charging device, a cleaning device and a developing device 20 constructed undetachable as shown in FIG. 2A. The life of the light-sensitive drum is to print about 15,000 sheets of paper and the life of the developing device is to process more than 50,000 sheets of paper. The toner box is designed to treat only 3,000 to 4,000 sheets of paper because the toner box becomes bigger to treat greater quantity and the bigger toner box creates inconveniences for users to handle. Accordingly, replacing the used toner box results in an uneconomical problem to scrap the usable light-sensitive drum and developing device all at once. To solve this problem, it is suggested to incorporate one unit comprising the light-sensitive drum, the cleaning device, and the charging device and the other one comprising the developing device 20 and the toner box 21 as shown in FIG. 2-b. However this solution also has an uneconomical problem to scrap the developing device when replacing the toner box 21.
On the other hand, another improvement is introduced to solve the above mentioned problems as shown in FIG. 2C. In this case, a light-sensitive drum 4, a cleaning device, and a charging device 5 are integrated in a unit. Further, a developing device and a toner box are detachably mounted. Accordingly, each unit can be replaced independently according to their respective life. But even if it is economical to use each device according to its life, it is difficult to perform maintenance and to repair work on this system.